A conventional fan rotor for compressing air comprises a disc having a plurality of radially extending blades mounted thereon. The fan blades are mounted on the disc by inserting the radially inner end of the blades in correspondingly shaped retention grooves in the radially outer face of the disc. The fan blades do not have platforms so the inner wall of an annulus for the compressed air is formed by fastening separate wall members to the radially outer face of the disc. The separate wall members bridge the space between pairs of adjacent blades to define the inner annulus wall.
It is known to fasten the wall members, defining the inner wall of the compressed air annulus, to the disc by feet which extend radially inwardly. The feet of the wall members engage complementary grooves, of dovetail cross-section, in the radially outer face of the disc. Fitting of the wall members is achieved by sliding the feet into the grooves in a direction axially of the disc.
This known method of attaching the wall members to the disc has the disadvantage that the grooves in the radially outer face of the disc have to be manufactured to within quite close tolerances to receive the feet of the wall members.
The present invention seeks to provide a rotor in which the inner wall of the flow annulus is defined by a plurality of wall members which are fastened to the disc in such away that grooves for their attachment are not required in the radially outer face of the disc.